The present invention relates to a service apparatus for quick printers (laser printers), particularly for receiveing, piling up and transferring continuous sheet material coming out of the laser printer. The data processing and their transfer onto paper by means of printing have been radically changed in the last 15 to 20 years, whereby today even modest data processing lines, such as for example electroaccounting centers, billing centers or invoice emitting centers and the like, are usually provided with a high speed printer like a laser printer. The printer is fed with a continuous band of paper, which hereinafter shall be also indicated as a continuous form, starting both from a reel and from sheet packages previously folded and prepared or provided with weakening lines for tearing or separating.
For a better understanding of the technical problems faced and solved by the present invention it seems advisable to shortly sum up the operations and processings which must be carried out on the paper.
The paper, which at the beginning is in a form of a reel of virgin or unused paper, is firstly provided with side holes serving for the purpose of dragging the paper through the several parts of the apparatus; these holes which are spaced by a unit pitch, are formed by means of perforating disks or cylinders having a number of punches peripherally protuding thereform. It is evident that this operation besides being a first operation carried out on the paper, is perfectly consistent with a constant and continuous advancement of the paper, such as that which takes place in the laser printing.
Then the paper, according to the prior art, is provided with weakening lines for a tearing or separation of adjacent parts. These lines are mainly crosslines, so as to individuate a series of forms by which the continuous band fed to the printer is formed. Besides these crosslines and other weakening lines can be added, such as for example those of the so-called self-enveloping forms, in which opening by tearing of edge strips is carried out. In all cases of cross weakening lines, the optimum condition for carrying them out is that of stopping. However, for a very short time, the paper is kept under a constant predetermined tension, while having it undergo the action of a crosswise perforator.
When it is not possible to stop the paper, a complicated mechanism was proposed, such as for example helicoidal blades which are crosswise positioned and rotate synchronously with the advancement of the paper.
The thus obtained paper is then folded, at the cross weakening lines, in order to permit it to be collected with an accordion like configuration to form a package with one sheet superimposed over the other, and the separation into a form of packages may be carried out either before or after they pass through a laser printer.
To date the perforating operation to provide the cross weakening lines and usually also the folding lines have been carried out upstream of the laser printer, preferably out of the feeding line of the printer.
In more recent years, and as a matter of fact from the beginning of the eighties, these centers have been provided with service apparatus (the so called servants) adapted to process the paper both before the entry into and after the exit from the printer.
More specifically, as regards the entry, there have been proposed and manufactured apparatus of two types depending on the manner in which the printer is fed, namely:
from a reel PA0 from a package.
Whereas for the first type, the continuous form is unwound from the reel, and for the second type, there have been proposed and manufactured apparatus to carry out the splicing between the last sheet or bottom sheet of a package, preferably already in the position for the feeding to the printer, and the first sheet or top sheet of the next package.
As examples of apparatus of this second type those disclosed in the European Patent No. 42619 and in the European Patent Application No. 86,101,511, owned by the same applicant, can be cited.
Turning now to the exit apparatus, their purpose is that of receiving the paper processed in the laser printer and pile it up into packages comprising a predetermined number of sheets. These packages are then transferred to the next processing steps, such as for example the tearing and the folding as an envelope for the mailing in the case for instance of self-enveloping bills or invoices.
It is evident that this apparatus may show and have which are not negligible problems due to the high speed by which the continuous form comes out of the laser printer (about 80 cm/s, corresponding to 1-4 sheets per second).
Secondly the problems are to be considered deriving from the passing of the paper within the laser printer, especially if of the so-called hot type, because the paper tends to be warped and bulged instead of being laid down in a planar and uniform manner onto an underlying sheet of the pile being formed. These problems and difficulties have originated a number of proposals for apparatus to overcome these problems among which are described in the U.S. Pat. Nos. 4,507,109, 4,618,340 and 4,650,447 of the same applicant can be cited.
These proposals are all based on the principle of collecting the paper coming in, and helping with the folding of the paper by means of bladed shafts, onto a receiving plane. The plane which can be gradually lowered as the height of the package being formed increases, and lowering takes place until a package having the desired size is formed, and thereafter, a cutting blade device carries out the cutting of the incoming paper band at a folding edge. Also above the cutting device a plane or equivalent member, in order to provide for a temporary support of the paper band continuously arriving from the printer, is interposed, thus permitting the transfer of the paper from the receiving plane of the finished package separated from the incoming paper. The essential problem which those apparatus had to face and solve was that of making the high speed and continuous working of the laser printer consistent with the several operations which are required both upstream and mainly downstream of the printer. Otherwise stated, owing to the fact that the primary and absolute requirement was and is that of "serving" the laser printer respecting its working rate, the service apparatus were based on the principle of maintaining the continuous advancement of the paper band which can not be stopped in a time period higher than a few seconds at a maximum. Consequently, the service inlet apparatus, for the splicing of subsequent packages of virgin forms, takes advantage from the package being fed to the printer as a storage or reserve to provide the time necessary for the splicing operation. In the case of the service exit apparatus, for which a greater number of complicated operations, as already mentioned, are necessary, the time necessary for their carrying out has been obtained by having recourse to the temporary supporting plane, positioned upstream of the position at which the operations of piling up, cutting and removal of the formed package take place. Obviously the fact that the paper can not be stopped even for short periods of time, is to a detriment of some operations. An example of the situation when the paper cannot be stopped are printing operations upstream or downstream of the laser printer which cause a dragging of the holes and the weakening of the lines or traces for the tearing or separating of adjacent sheets. These can be carried out only by recourse to mechanisms which are complicated but also mainly require operation with a strict synchronism with respect to the other component parts of the machine. This, as a matter of practice, results in a reduced reliability and above all readily undergoing stopping both due to the loss of synchronization and due to operations such as size changes requiring the substitution of gears or their adjustment. All that is obviously not consistent with the service requested in the case of a laser printer whereby as already mentioned these operations have been to date carried out separately.
For other operations, such as a cutting and a removal of a finished package, on the contrary, the apparatus, in order to achieve the given purposes, is very complicated from a mechanical point of view and requires very strict synchronism. As known to every skilled technician, the machines of this type may readily undergo a jamming and consequently require a frequent maintenance and assistance, resulting in high operation costs while adding to of the intrinsic cost of the apparatus which is not negligible.
The above mentioned apparatus according to the prior art moreover has a not negligible encumbrance, whereby to provide a laser printer with a service apparatus both at the entry side and the exit side means to create a line of relevant proportions, which are not always consistent with the requirements of the user and with the available room. On the other side the provision of an apparatus which:
(1) has a reduced encumbrance together with a greater functionality;
(2) is able to operate starting both from reel and from packages;
(3) has reduced mechanical complexity and greater flexibility;
(4) besides the essential operations of piling up of the continuous form as a package, separation and remowal thereof, permits other operations as the standard printing of the continuous form, for instance in a number of colours either upstream or downstream of the laser printer, the carrying out of the weakening lines used for the tearing in line with the laser printer, and the like; and
(5) in the same encumbrance of the exit service apparatus combine also the entry service apparatus as regards the splicing of subsequent packages, is a very desirable industrial target.
These purposes are achieved with the present invention on the basis of a totally different operating principle. One is to decompose the substantially continuous and unbroken motion of the continuous form through the laser printer into a succession of pulse motions consisting of unit advancements and stops of the paper band downstream of the laser printer, and if necessary upstream thereof. For advancements the paper is under control both as regards the length which is being advanced in each unit advancement and as regards the speed at which such an advancement occurs. The stops are exploited to carry out single operations, such as for example tearing of the tie part used for tying of the finished package, by tearing the tie from the band arriving from the laser printer, with the provision that each stop has a duration less than the maximum stop time permitted for the laser printer without it entering the phase of self cleaning maintenance. This time is of the order of some seconds, usually 4.5 seconds.
According to a first feature, thus, the present invention consists in an operating method for a service apparatus for laser printers. The service apparatus is of the type comprising a base or lower part, dragging means for the paper band entering the apparatus and coming from the laser printer means for advancement of the paper band from the laser printer to a receiving plane for piling up the sheets forming the paper band into or as a package, means for separation of the last sheet of the package being completed from the upstream band, and means for the folding of paper before the piling up onto said receiving plane, preferably when the laser printer is fed from a reel. The operating method provides for the dragging means to be intermittently actuated for predetermined times with intervals of stopping times which are also strictly predetermined.
According to the preferred embodiment of the present invention said dragging means consist of a form dragging device or tractor of a standard type, driven by motor means, preferably consisting of a stepping motor. Control means is provided for the motor means in order to actuate them in a pulse manner for intervals of strictly predetermined duration and stop them for times which are strictly predetermined as well in order to carry out required operations on the paper coming from the laser printer occurring during said stopping times of said motor means. The service apparatus according to the present invention in turn is characterized in that:
1) said means for the separation of the last sheet of the package being complete from the paper band coming from the laser printer consist of a tearing mechanism comprising means controllably engageable with the paper band in order to retain it in an area upstream of a predetermined pre-formed weakening cross-line, means for the frictional advancement of the band, roller means which can be engaged under control with a side band in an area downstream of said predetermined weakening cross line and deviating means adapted to hit the side band at said predetermined weakening cross line;
2) said folding means comprise a member oscillating around a horizontal axis for a predetermined angle in both directions, having a passage in which said paper band coming from said tearing means is vertically advanced, first comb-like or toothed means against which said oscillating member abuts at the end of the oscillating arc, whereby the paper band is retained between said oscillating member and the said first comb means, and the second comb or toothed means adapted to oscillate around a horizontal axis between a first rest position and a second operating position in which said second comb means abut against said oscillating member whereby the paper band is clamped in a position downstream with respect to the clamping position between said first comb means and said oscillating member, and consequently the paper is folded with an acute edge around the edge of said oscillating member;
said apparatus furthermore comprising:
3) cage means receiving the band coming out of said folding means, the bottom of which is formed by said receiving plane, movable by means of motor means between a raised initial position and a lowered final position; the cage is moreover defined by two side walls, parallel to the folding edge of the paper, formed by vertical, parallel and spaced rods, which can be simultaneously displaced in the direction of mutual approaching and removal with respect to the center or mid line of said receiving plane coincident with the laying plane of the paper band passing through said tearing means, each of said walls having rigidly connected thereto a pressing member adapted to engage from above the edge of at least one sheet just laid down onto said receiving plane; and the pressing members are actuated by means for alternated movements of pressing and withdrawal;
4) switch means fixed to at least one of said side walls and actuable from means rigidly connected to said pressing means in their pressing stroke, and the switch means is adapted to control the lowering movements of said receiving plane;
5) ejecting means for the packages piled up onto said receiving plane which can be crosswise displaced with respect to said receiving plane in a direction parallel to said laying plane of the paper band;
6) a splicing mechanism for the packages being fed to the laser printer comprising a frame forming the upper surface of the apparatus, said frame comprising a pair of conveying belts having the upper surfaces parallel and coplanar, each conveying belt being closed to itself and actuated by autonomous motor means for the displacement in the same direction for each belt, a stationary splicing area being provided between said conveying belts comprising at the first end fixed means for the temporary anchoring of the two sheets to be spliced and towards the opposite end displaceable plate means having second temporary anchoring means for said two sheets to be spliced, cutting means mounted at both sides and symmetrically with respect to said first and second anchoring means, adhesive tape supporting and unwinding means such that a strip of adhesive tape can be unwound parallely to the splicing line between said two sheets positioned with the approached ends, and guide and positioning means for said strip of adhesive tape consisting of two V shaped gorges, the apex of which is flush and aligned with said splicing line, the flanks of said gorge being coated with anti-adhesive material, and motor means for the translation of said frame between a first position in which it forms the upper cover of said exit service apparatus and a second position in which it is displaced towards one end in a cantilevered manner, so as to uncover and give access to said exit service apparatus;
7) a cross perforation device, mounted upstream of said dragging means to act onto the paper band arriving from the laser printer, comprising a perforating blade having a saw-toothed cutting edge and preferably formed with a curved shape with its convexity directed towards the paper to be perforated, actuating means connected at both ends of said blade and subjected to a vertical alternating movement whereby the lowering of one end corresponds to the raising of the other end and viceversa. The particular features and advantages of the present invention shall more clearly appear from the following detailed description, made with respect to the enclosed drawings, of a preferred embodiment, which have an exemplifing but not a limiting purpose.